Real-time calibration algorithm for phase shifting in phase-measuring profilometry

A new real-time calibration algorithm for phase shifting based on the fast Fourier transform (FFT) is presented. The purpose of this algorithm is to d etermine the phase shift between two fringe images rapidly and accurately. In it, the background distributions of two current fringe images are remove d by recording additional fringe data with arbitrary phase shifts delta. Th us, the phase shift between these two fringe patterns can be obtained corre ctly by the FFT method. With the help of an adaptive bandpass filter and a new modulation function defined in this paper, the accuracy of the phase-sh ift determination is further improved. By this method, we can simultaneousl y control the phase shift of the projection grating. The accuracy and the a utomation of the PMP system are enhanced greatly. (C) 2001 Society of Photo -Optical Instrumentation Engineers.